Turbocharged engines often employ bypass devices such as wastegate valves to regulate a turbocharger speed and a resulting boost pressure of air delivered to an intake of the engine. Wastegate valves generally include a valve element disposed within an exhaust system of the engine, and a pneumatic actuator used to move the valve element. The pneumatic actuator selectively moves the valve element to modify a volume of exhaust gases directed into or bypassed around a turbine of the turbocharger. Boost air pressure is directly supplied from a compressor of the turbocharger to the pneumatic actuator to control movement of the connected valve element. As boost air pressure increases, a force of the pneumatic actuator gradually urges the valve element to open, thereby bypassing a greater amount of exhaust around the turbine and lowering turbocharger speed and boost air pressure. As boost air pressure decreases, the pneumatic actuator returns the valve element toward a closed position such that more exhaust passes through the turbine, thereby increasing turbocharger speed and boost air pressure.
Although effective at regulating the speed of the turbocharger and the resulting boost air pressure, wastegate and other pneumatic engine valves can be exposed to very high exhaust temperatures. These temperatures create a harsh environment for the pneumatic actuator and the valve element that may decrease their useful lives.
One attempt to prolong the life of a wastegate valve is described in U.S. Pat. No. 4,463,564 (the '564 patent) to McInerney, issued Aug. 7, 1984. Specifically, the '564 patent discloses a turbine housing assembly for use with a turbocharger having an exhaust gas driven turbine wheel for rotatably driving a compressor impeller. The assembly includes a turbine housing having an exducer passage into which exhaust gases are discharged from the turbine wheel. A bypass passage in the turbine housing and a pivoting wastegate valve cooperate to provide an exhaust ejector for drawing gases through the exducer passage. The turbine housing further includes a vent for circulation of ambient air between the bypass and exducer passages. The air vent improves cooling of the turbine housing between the bypass and exducer passages.
Although the air vent of the '564 patent may improve cooling of the turbine housing, it may be insufficient for some applications. In particular, the use of ambient air, because of its temperature, may be minimally successful at cooling the turbine housing in extreme temperature applications. In addition, the cooling of the turbine housing may have little effect on the temperature of the wastegate valve or an associated actuator that are separated from the turbine housing.
The valve of the present disclosure is directed towards solving one or more of the problems set forth above and/or other problems of the prior art.